loophole (n.)
- abatis
- alternative
- armhole
- avenue
- bank
- banquette
- barbican
- barricade
- barrier
- bastion
- battlement
- beacon
- belvedere
- bleachers
- blowhole
- breastwork
- bridge
- bulwark
- bunghole
- channel
- cheval-de-frise
- choice
- chute
- cringle
- curtain
- deadeye
- dike
- dodge
- door
- drawbridge
- earthwork
- egress
- enclosure
- entanglement
- escape
- escarp
- escarpment
- estuary
- evasion
- exhaust
- exit
- eye
- eyelet
- fence
- fieldwork
- floodgate
- flume
- fortification
- gallery
- gasket
- gazebo
- grandstand
- grommet
- guide
- keyhole
- knothole
- lighthouse
- lookout
- loop
- lunette
- machicolation
- manhole
- mantelet
- merlon
- mound
- observatory
- opening
- out
- outcome
- outfall
- outgo
- outlet
- outlook
- outwork
- overlook
- palisade
- parapet
- peephole
- pharos
- pigeonhole
- pinhole
- placket
- pore
- port
- portcullis
- porthole
- pretext
- quibble
- rampart
- redoubt
- ringside
- scarp
- sconce
- sluice
- spiracle
- spout
- stockade
- subterfuge
- tap
- tower
- vent
- venthole
- vomitory
- watchtower
- weir
- work
